Concrete Superstructure
Section 2300
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The work shall cover furnishing and providing of concrete superstructure in
accordance with the drawings as per these specifications or as directed by the
Engineer.
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Materials shall conform to Section 1000 of these Specifications.
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2303.1. A method statement for construction, indicating the following, shall be
submitted by the Contractor for approval of the Engineer, well in advance of the
commencement of the construction of superstructure :
i)
Sources of Materials
ii)
Design, erection and removal of formwork
iii)
Production, transportation, laying and curing of concrete
iv)
Prestressing system if applicable
v)
Personnel employed for execution and supervision
vi)
Tests and sampling procedure
vii)
Equipment details
viii)
Any other point
2303.2. Dimensions, lines and levels shall be set out and checked with respect to
permanent reference lines and permanent bench mark so that the final product is in
accordance with the drawings or as directed by the Engineer.
2303.3. The work shall conform to the following sections besides stipulations in this
section with regard to specific type of construction:
i)
Formwork
Section 1500
ii)
Steel Reinforcement
Section 1600
iii)
Structural Concrete
Section 1700
iv)
Prestressing
Section 1800
Additionally, some of the common types of superstructure construction shall have features as
discussed in this Section.
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2304.1. Solid Slabs
Where adjacent span of slab has already been cast, the expansion joint and filler
board shall be placed abutting the already cast span which shall form the shutter on
that side of the new span to be cast. The whole of the slab shall be cast with
reinforcement embedded for the road kerb and railings. No other construction joint
shall be allowed except with the express permission of the Engineer.
Where wearing -coat is required to be provided, after the deck slab has been cast,
the surface of the slab shall be finished rough, but true to lines and levels as shown
on the drawings, before the concrete has hardened. The areas of construction joints
shall be treated in the prescribed manner.
The top of the slab shall be covered with clean moist sand as soon as the top
surface has hardened. Curing shall be carried out as per Section 1700.
Where the slab is resting on bearings, the same shall be placed in position in
accordance with the drawings, before casting of deck slab.
23.04.2. RCC T-Beam and Slab
Provision of construction joint
the Engineer. No construction
web. If not indicated on the
junction of the web and the
permission of the Engineer.
shall conform to the drawings or as per directions of
joint shall be provided between the bottom bulb & the
drawing, construction joint may be provided at the
fillet between the web and the deck slab with the
The portions of deck slab near expansion joints shall be cast alongwith
reinforcements and embedment for expansion joints, For this purpose, the portion of
deck slab near expansion joints may be cast in a subsequent stage, if permitted by
the Engineer.
The surface finish of the deck slab shall be finished rough but true to lines and levels
as shown on the drawings before the concrete has hardened. Care shall be taken
for setting of bearings as indicated on the drawings.
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2305.1. PSC Girder and Composite RCC Slab
PSC Girder may be precast or cast-in-situ as mentioned on the drawing or as
directed by the Engineer. Girders may be post-tensioned or pre-tensioned. Where
precast construction is required to be adopted, selection of casting yard and details
of methodology and of equipment for shifting and launching of girders shall be
included in the method statement.
In case of cast-in-situ construction, the sequence of construction including side
shifting of girders, if applicable, and placing on bearings shall be in accordance with
the drawings.
The PSC girder constituting the top flange, web and the bottom flange shall be
concreted in a single operation without any construction joint.
The portions of deck slab near expansion joints shall be cast alongwith
reinforcements and embedment for expansion joints. For this purpose, the portion of
deck slab near expansion, joints may be cast in a subsequent stage, if permitted by
the Engineer.
The surface finish of the deck slab shall be finished rough but true to lines and levels
as shown on the drawings before the concrete has hardened. Care shall be taken
for setting of bearings as indicated on the drawings.
2305.2. Box Girder
Box girders may be simply supported or continuous. Simply supported box girders
shall have minimum construction joints as approved by the Engineer. In the case of
continuous box girders the sequence of construction and location of construction
joints shall strictly follow the drawing.
The box section shall be constructed with a maximum of one construction joint
located in the web below the fillet between the deck slab and web. If permitted by
the Engineer, one additional construction joint may be permitted and this
construction joint shall, be located in the web above the fillet between the soffit slab
and web.
The portions of deck slab near expansion joints shall be cast alongwith
reinforcements and embedment for expansion joints. For this purpose, the portion of
deck slab near expansion joints may be cast in a subsequent stage, if permitted by
the Engineer.
The surface finish of the deck slab shall be finished rough but true to lines and levels
as shown on the drawings before the concrete has hardened. Care shall be taken
for setting of bearings as indicated on the drawings.
2305.3. Cantilever Construction
Continuity of untensioned reinforcement from one segment to the next must be
ensured by providing full lap length as necessary.
The design of the superstructure shall take into account the following aspects,
which form an integral part of the construction operations
a)
Stability against over-turning for each statical condition, through which the assembly
passes, shall be checked.
b)
Stresses at each preceding segment joint with the addition of every segment or
change of statical conditions shall be checked. The load of equipment as well as
construction live load shall be taken into account.
c)
Precambering of the superstructure during construction shall be done in such a
manner that the finally constructed structure under permanent load attains the final
profile intended in the drawings.
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2306.1. Precast Concrete Superstructure
Variation in cross-sectional dimensions
a) upto and including 2m
over 2m
:
:
± 5 mm
± 5 mm
b) Variation in length overall and length between
bearings
:
shall not exceed ± 10 mm
or 0.1 ± per cent of the span
length. Whichever is lesser
:
5 mm
a) Variations in, thickness of top and bottom slab
for box girders, top and bottom flange for
T-girders or slabs
:
-5 mm to +10 mm
b) Variations in web thickness
:
-5 mm to +10 mm
c) Variations in overall depth or width
:
± 5 mm
d) Variation in length overall and length between
bearings
:
shall not exceed ± 10mm
or ± 0. 1 per cent of the
span length, whichever is
lesser
e) Permissible surface irregularities when
measured with a 3 m straight edge or template
:
5 mm
c) Permissible surface irregularities when measured
with a 3 m straight edge or template
2306.2. Cast-in-Situ Superstructure
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The materials shall be tested in accordance with these specifications and shall meet
the prescribed criteria.
The work shall conform to these specifications and shall meet the prescribed
standards of acceptance.
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Concrete in superstructure shall be measured in accordance with Section 1700,
based on the quantity ordered or as shown on the drawings.
Steel reinforcement (untensioned) in superstructure shall be measured in
accordance with Section 1600, based on the quantity ordered or as shown on the
drawings.
High tensile steel (prestressing) in superstructure shall be measured in accordance
with Section 1800, based on the quantity ordered or as shown on the drawings.
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The contract unit rates for concrete, steel reinforcement (untensioned) and high
tensile steel (prestressing) shall include all works as given in respective sections of
these specifications and cover all incidental items for furnishing and providing
superstructure as mentioned in this section.